(1) Field of the Invention
The present invention relates to a control method and a control apparatus of a direct injection gasoline engine, and more specifically, to a control technique of the injection timing and ignition timing in a direct injection gasoline engine comprising a fuel injection valve for directly injecting fuel into a cylinder.
(2) Related Art of the Invention
Conventionally, a direct injection gasoline engine comprising a fuel injection valve for directly injecting fuel into a cylinder is known comprising a stratified charge combustion mode for performing a stratified charge combustion by carrying out fuel injection only in a compression stroke, a uniform charge combustion mode for performing a uniform charge combustion by carrying out fuel injection only in an intake stroke, and a double injection mode for performing a fuel injection in the intake stroke and a fuel injection in the compression stroke during one cycle, wherein either one of the stratified charge combustion mode or the uniform charge combustion mode is selected in correspondence to the driving condition, and on the other hand, the double injection mode is carried out during the switching time between the stratified charge combustion mode and the uniform charge combustion mode (refer to Japanese Unexamined Patent Publication No.5-071383).
Obviously, the requested injection timing differs between the stratified charge combustion mode and the uniform charge combustion mode, and the appropriate ignition timing also differs. Therefore, in the prior art, the injection timing was set for each of the combustion modes, and the ignition timing was set with different properties for each of the combustion modes.
When the intake stroke injection was performed in the double injection mode, it was controlled according to the injection timing and the ignition timing of the uniform charge combustion mode, and when the compression stroke injection was performed in the double injection mode, it was controlled according to the injection timing and the ignition timing of the stratified charge combustion mode.
However, experiments showed that it was not always possible to gain a high combustion stability with the conventional structure where the injection timing and the ignition timing according to the uniform charge combustion mode or the stratified charge combustion mode were utilized as it is for the injection timing and the ignition timing of the double injection mode.